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https://www.askthetrades.co.uk/cgi-bin/yabb/YaBB.pl DIY Forum >> Electrical Questions >> memera 2000 https://www.askthetrades.co.uk/cgi-bin/yabb/YaBB.pl?num=1379083893 Message started by aly on Sep 13^th, 2013, 3:51pm

Title: memera 2000
Post by aly on Sep 13^th, 2013, 3:51pm

hi need to replace a fuse in my fuse box but can't get old one out .have switched off main switch and pulled but it will not budge . please help is there a trick to doing this.

Title: Re: memera 2000
Post by Lectrician on Sep 13^th, 2013, 3:55pm

Assuming its one of these:

It should pull out pretty easily.

If it has overheated, it my be "welded" shut. Do you know it's blown, or are you assuming? Perhaps it has overheated due to a loose connection inside.

Title: Re: memera 2000
Post by CWatters on Sep 16^th, 2013, 6:50am

Sorry if it's a silly question but... Have you released the DIN rail catch? The photo Lectrician posted shows two of these in the unlatch position (I think). You will probably have to remove a bus bar as well.

Title: Re: memera 2000
Post by scotspark on Sep 16^th, 2013, 4:19pm

thats just a terminal screw cover CW

no need to remove any screws to change a fuse.

unless its welded and you need to change carrier that is.

Title: Re: memera 2000
Post by CWatters on Sep 17^th, 2013, 7:42am

My mistake. I have a different CU and the MCB don't just pull out if that's what you are trying to do.

Title: Re: memera 2000
Post by Lectrician on Sep 17^th, 2013, 5:14pm

These are not MCBs, they are HRC fuse carriers. The module is identical to an MCB in size and it fits to the dinrails in the same way. To swap a fuse, you pull the carrier out. The assembly stays on the dinrails/busbar.

Title: Re: memera 2000
Post by The_Trician on Oct 27^th, 2013, 1:18pm

LEC,
Where can those MEM Fuse carriers be had from?

I have a MEMSHIELD 2 3 phase board which feeds 3 single phase consumer units in a local hotel via 40A type B mcbs. I am thinking that these do not provide proper fault discrimination with the individual consumer unit mcbs and would like to swap em out for Fuses instead.

I've looked and looked but have never found any available before.

TT

Title: Re: memera 2000
Post by scotspark on Oct 27^th, 2013, 2:07pm

quick google

http://www.ebay.co.uk/bhp/memera-fuses

http://www.ebay.co.uk/sch/i.html?_kw=memera+2000+hrc+fuse+mem

http://www.ebay.co.uk/bhp/mem-memera

http://www.ebay.co.uk/bhp/mem-fuse-carrier

don't know if they are suitable for 3 phase boards.

the commercial mcb's fitted in domestic boards but the domestic mcb's didn't fit in the commercial boards.

Title: Re: memera 2000
Post by Lectrician on Oct 27^th, 2013, 3:12pm

They are no longer available from new. The 45amp ones take up two ways. They would fit the TP boards (it was the newer AD MCB's that would not bit the commercial boards due to narrower busbars/terminals on the newer AD models).

A C type MCB is always preferable on sub-mains. What size cable is it? Could you go up from a 40?

Title: Re: memera 2000
Post by Lectrician on Oct 27^th, 2013, 3:14pm

scotspark wrote on Oct 27^th, 2013, 2:07pm:

Only the second link there would be any good ;)

This is the larger ones:

This is the normal din sized:

Title: Re: memera 2000
Post by The_Trician on Oct 27^th, 2013, 9:11pm

The submains from the 3 ph board are run in what in looks like 16mm T&E so am thinking around 50A max. Might get away with 63a but without checking I can't say for certain.
Am thinking Zdb + Zs at C/U subccts might be exceeded if we go any higher.

Title: Re: memera 2000
Post by scotspark on Oct 28^th, 2013, 6:30pm

why would sub ccts be affected by the submains mcb/fuse?

Title: Re: memera 2000
Post by Lectrician on Oct 28^th, 2013, 6:53pm

Poor discrimination on magnetic (not thermal) trip side. Get a short on the sockets, and you could trip the submain, not the final circuit.

Title: Re: memera 2000
Post by scotspark on Oct 29^th, 2013, 8:36pm

Yes I understand tha lec

The_Trician wrote on Oct 27^th, 2013, 9:11pm:

The submains from the 3 ph board are run in what in looks like 16mm T&E so am thinking around 50A max. Might get away with 63a but without checking I can't say for certain.
Am thinking Zdb + Zs at C/U subccts might be exceeded if we go any higher.

Its this part I didnt get?

The sub cct either complies or it doesnt?

upgrading the supply fuse to the board makes no difference.

Title: Re: memera 2000
Post by Lectrician on Oct 29^th, 2013, 9:18pm

See what you mean.

The Zdb at the sub board would have to meet the max Zs for the C type or HRC fuse being fitted to protect the submain, but the final circuits from the submain would not be affected, they have their own overcurrent devices, and their own max Zs figures.

Title: Re: memera 2000
Post by scotspark on Oct 30^th, 2013, 10:16pm

Exactly.

TT only needs to worry about the sub main cct he is upgrading the fuse/mcb on